JP2019099414A - Silica glass member and manufacturing method of silica glass member - Google Patents

Abstract

To provide a silica glass member achieving low thermal expansion required when miniaturization of a device is conducted using a multi patterning by setting fluorine concentration at a prescribed concentration range in a zone from a surface to a prescribed depth, and a manufacturing method of the silica glass member.SOLUTION: The silica glass member is a silica glass used in an optical lithography process with a vacuum ultraviolet light as a light source. Content of fluorine is 1.0 wt.% to 5.0 wt.% in a zone from a surface of a silica glass surface vertical to a transmission direction of a lithography light to 50 μm.SELECTED DRAWING: None

Description

  The present invention relates to a silica glass member and a method for producing a silica glass member, for example, a silica glass member and a silica glass member for a photomask which can be used for photolithography in a vacuum ultraviolet wavelength region using an ArF excimer laser as a light source. It relates to the manufacturing method.

  In recent years, in lithography technology, the demand for miniaturization of semiconductor devices has been increasing more and more, exposure has been shortened by shortening the exposure wavelength, or by immersion exposure technology in which pure water or the like is immersed between the lens and the wafer. A method of increasing the numerical aperture of the lens to be used is adopted.

  Assuming that the wavelength of exposure light is λ, the numerical aperture representing the lens performance of the exposure apparatus is NA, and the process constant is k1, the resolution R in photolithography can be expressed by the equation R = k1λ / NA, and the exposure wavelength λ is The resolution can be improved by reducing the process constant k1 while shortening the numerical aperture NA.

  Here, the exposure wavelength λ starts from the g-line (436 nm) of a mercury lamp, and so far i-line (365 nm), KrF excimer laser (248 nm) and ArF excimer laser (193 nm) are used to shorten the light source Has been advanced.

  The numerical aperture NA geometrically represents the size of the lens, and when the exposure light is narrowed by the lens and imaged on the wafer surface, NA = n · sin θ (n is a medium between the lens and the wafer The refractive index of, θ represents the opening angle of the light beam.

Here, when the medium between the lens and the wafer is air, the refractive index n = 1.0, but when this medium is changed to pure water, the refractive index of water to the ArF excimer laser wavelength is 1.44. Therefore, NA takes a value of 1.44 at the maximum.
In reality, the opening angle is not 0 degree, so NA can take a value of about 1.35.

The kl factor is called a process constant determined by the optical system and resist performance, and the theoretical limit is 0.25.
Therefore, by using an ArF excimer laser with an exposure light wavelength of 193 nm and using an immersion exposure technique, it is possible to achieve a resolution of 43 nm with a numerical aperture of 1.35 and a kl factor of 0.3.

  And, as a member for photolithography using this ArF excimer laser, a silica glass member is suitably used because it is excellent in low thermal expansion and light transmission.

By the way, when the device is miniaturized using multi-patterning, if the exposure of the position of the target pattern can not be performed with high accuracy, a pattern shift will occur, so an extremely high pattern can be obtained between multiple times of lithography. Therefore, the silica glass substrate (silica glass member) for a photomask has a lower thermal expansion than that of a conventional silica glass substrate in order to avoid positional deviation due to thermal expansion during exposure. It is required to be.

For example, the overlay accuracy of double patterning exposure is the sum of the overlay accuracy of two exposures, and the overlay accuracy required for each exposure is said to be about 3 to 4 nm. The thermal expansion coefficient of normal silica glass is 5.0 × 10 ^{-7 to} 6.0 × 10 ^-7 / K, and the required accuracy is obtained because a 1 cm quartz piece has an elongation of 5 to 6 nm as the temperature rises by 1 K. It is hard to say that it is enough for

For this reason, thermal expansion is required to be smaller than ordinary silica glass, and silica glass having a thermal expansion coefficient of 4.0 × 10 ⁻⁷ or less, preferably 3.0 × 10 ⁻⁷ or less is required. ing.
For example, in Non-patent Document 1 (Development of optical fibers in Japan (1989)), it is shown that the thermal expansion at 400 ° C. is reduced by doping fluorine in the range of 1.3 wt% or less. It is also described that the slow cooling rate also affects the thermal expansion.

Further, in Patent Document 1 (Japanese Patent Laid-Open No. 2000-239040), the OH group concentration is 5 ppm or less, the fluorine concentration is 0.1 to 2 mol%, and the hydrogen concentration is 5 × 10 ¹⁶ molecules / cm ³ or less. A synthetic quartz glass material and an optical member for an F ₂ excimer laser optical member are shown. In addition, as a method of doping fluorine, it has been shown that a porous body called a soot of silica glass is produced by the VAD method, and then fluorine is doped during heat treatment in a gas atmosphere of a fluorine compound.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-342034) has an OH group concentration of 0.5 ppm or less, a fluorine concentration of 0.1 to 2 mol%, a hydrogen molecule concentration of 5 × 10 ¹⁶ molecules / cm ³ or less, a fluorine concentration The synthetic quartz glass optical material for F ₂ excimer laser is characterized in that the difference between the maximum value and the minimum value is within 20 mol ppm and the difference between the maximum value and the minimum value of the refractive index is 2 × 10 ^-5 or less. It is done.
According to Patent Document 3 (Japanese Patent Laid-Open No. 2001-180956), the maximum value of fluorine concentration is 100 ppm or less, the difference between the maximum value and the minimum value is 50 ppm or less, and the concentration of OH group and chlorine in the light use region. Synthetic quartz glass is shown where the maximum is less than 10 ppm each.

  Then, in Patent Documents 2 and 3, as a method of doping fluorine, a porous body called a soot of silica glass is produced by the VAD method as in Patent Document 1, and then heat treatment is performed in a gas atmosphere of a fluorine compound. It has been shown to dope fluorine. Moreover, in order to make a fluorine concentration uniform as the whole silica glass, passing through processes, such as adjustment of a fluorine concentration, and an annealing treatment, is shown.

JP, 2000-239040, A JP 2001-342034 A JP 2001-180956 A

Development of optical fibers in Japan (1989)

  As described above, in Patent Documents 1 to 3, a synthetic quartz glass member (silica glass member) in which the entire silica glass member has a substantially constant fluorine concentration and the fluorine concentration is 0.1 to 2 mol% It is shown.

However, in order to obtain these synthetic quartz glass members (silica glass members), it is necessary to use a large amount of fluorine compound gas in order to dope the whole of the silica glass members. was there.
In addition, in order to make the fluorine concentration substantially constant as a whole of the silica glass, there is a technical problem that it is necessary to go through complicated processes such as adjustment of the fluorine concentration and annealing treatment.

In order to solve technical problems, the present inventor has intensively studied a thermal expansion synthetic quartz glass member (silica glass member) which is required in the case of miniaturizing a device by using multiple patterning.
In the case of this research, first, when the silica glass member for a photomask is used for photolithography using an ArF excimer laser as a light source, a pattern film and a silica glass member formed on the surface of the silica glass member are used. It was found that the surface area was raised to the highest temperature by the laser light at first.
Then, the inventor considered that reducing the thermal expansion of the surface layer was the most important to avoid an unintended pattern deviation at the time of exposure.

  Furthermore, when the fluorine concentration is in the predetermined concentration range in the region from the silica glass surface to the predetermined depth, the present inventor has low thermal expansion which is required when the device is miniaturized using multi-patterning. We found out what we could achieve. In addition, it has been found that the thermal expansion of the surface layer of silica glass can be reduced by performing the fluorine doping treatment by a simple method, and the present invention has been completed.

The present invention has been made to solve the above technical problems, and in the case where the device is miniaturized using multi-patterning by setting the fluorine concentration to a predetermined concentration range in the region from the surface to the predetermined depth. It is an object of the present invention to provide a silica glass member achieving the low thermal expansion required for
Further, the present invention has been made to solve the above technical problems, and to provide a method for producing a silica glass member for setting the fluorine concentration to a predetermined concentration range in the region from the surface to the predetermined depth. To aim.

  The silica glass member according to the present invention made to solve the above technical problems is a silica glass used in a photolithographic process using vacuum ultraviolet light as a light source, and the silica glass perpendicular to the transmission direction of the lithography light It is characterized in that the content of fluorine is 1.0 wt% or more and 5.0 wt% or less in a region from the surface of the surface to 50 μm.

  As described above, since the fluorine content is 1.0 wt% or more and 5.0 wt% or less in the region from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light to 50 μm, the device using multi-patterning It is possible to achieve low thermal expansion which is required when performing miniaturization. That is, since the thermal expansion of the surface layer is suppressed, it is possible to avoid an unintended pattern displacement at the time of exposure.

Specifically, the thermal expansion coefficient at 20 ° C. to 50 ° C. may be 4.0 × 10 ⁻⁷ / K or less in a region from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light to 50 μm. it can.

The OH group concentration is preferably 10 ppm or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.
The fluorine concentration and the OH group concentration are in a trade-off relationship, and by setting the OH group concentration to 10 ppm or less, the fluorine concentration in the region from the surface of the silica glass surface to 50 μm is 1.0 wt% to 5.0 wt% can do.

The width of the maximum value and the minimum value of the fluorine concentration is preferably 100 ppm or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.
When the width of the maximum value and the minimum value of the fluorine concentration in the region up to 50 μm from the surface of the silica glass surface exceeds 100 ppm, a partial difference in thermal expansion occurs, which is not preferable.

The fictive temperature is desirably 1000 ° C. or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.
Since the fictive temperature is 1000 ° C. or less, it is preferable because the residual stress becomes uniform and uniform expansion is achieved.

  Moreover, the linear transmittance of light with a wavelength of 193 nm is 90% or more, and the silica glass member is preferable. Since the linear transmittance of light is 90% or more, it can be suitably used in the photolithography process.

  Further, the method for producing a silica glass member according to the present invention made to solve the above technical problems comprises the steps of producing silica glass which is a transparent vitrified dense body, and transmitting the lithography light to the silica glass. Heat treatment in a fluorine compound gas atmosphere and under pressure so that the fluorine content is 1.0 wt% or more and 5.0 wt% or less in a region from the surface of the silica glass surface perpendicular to the direction to 50 μm, doping with fluorine It is characterized by including a process and the annealing treatment process heated at less than 1000 ° C in the atmosphere after the above-mentioned fluorine doping process.

  The present invention is characterized in that silica glass, which is a transparent vitrified dense body, is heat-treated in a fluorine compound gas atmosphere and under pressure to dope the fluorine, and the fluorine content is 1 in the region up to 50 μm from the surface A silica glass member having a content of not less than 0 wt% and not more than 5.0 wt% can be obtained relatively easily.

According to the present invention, it is possible to obtain a silica glass member achieving the low thermal expansion which is required when miniaturizing a device by using multi-patterning.
Moreover, according to this invention, the manufacturing method of the silica glass member which can manufacture the said silica glass member easily can be obtained.

The silica glass member of the present invention is characterized in that the fluorine content is 1.0 wt% or more and 5.0 wt% or less in a region from the surface of the silica glass surface perpendicular to the transmission direction of lithography light to 50 μm. .
Thus, the thermal expansion of the silica glass surface or surface layer is reduced by containing a specific amount of fluorine in the region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the soographic light, and unintended at the time of exposure Pattern deviation can be avoided.

  Here, it is not preferable to use a region up to 50 μm from the surface of silica glass because fluorine doping to a region exceeding 50 μm is likely to result in an increase in the size of the device and increase in manufacturing cost. Moreover, it is necessary to go through complicated manufacturing processes, which is not preferable.

  Here, the content of fluorine in the range exceeding 50 μm from the surface of silica glass is lower than the fluorine material in the region from the surface up to 50 μm depending on the depth. The content is about 0.25 wt% or less in general, and even when not substantially contained, there is no influence on pattern deviation at the time of exposure.

The OH group concentration is preferably 10 ppm or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.
The fluorine concentration and the OH group concentration are in a trade-off relationship, and by setting the OH group concentration to 10 ppm or less, the fluorine concentration in the region from the surface of the silica glass surface to 50 μm is 1.0 wt% to 5.0 wt% can do.

Further, it is preferable that the width between the maximum value and the minimum value of the fluorine concentration is 100 ppm or less in a region from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light to 50 μm.
When the width of the maximum value and the minimum value of the fluorine concentration in the region up to 50 μm from the surface of the silica glass surface exceeds 100 ppm, a partial difference in thermal expansion occurs, which is not preferable.

  The maximum value of the fluorine concentration refers to the maximum value of the fluorine concentration measured at each point of the use area used for photolithography. The minimum value of the fluorine concentration means the minimum value of the fluorine concentrations measured at each point of the use area. Further, the range between the maximum value and the minimum value of the fluorine concentration means the difference between the maximum value and the minimum value of the fluorine concentration.

In order to make the thermal expansion of the silica glass surface layer ^{4.0.times.10.sup.-7} / K, it is desirable to make the fictive temperature 1000.degree. C. or less. When the fictive temperature is higher than 1000 ° C., distribution of residual stress is likely to occur, which may cause a partial difference in thermal expansion.
The virtual temperature can be determined based on the formula reported in Journal of Non-Crystalline Solids vol. 185 (1995) p. 191.

The silica glass member according to the present invention has a thermal expansion coefficient of 4.0 × 10 ⁻⁷ / K at 20 ° C. to 50 ° C. in the region from the surface of the silica glass surface perpendicular to the transmission direction of lithography light to 50 μm. The linear transmittance of light with a wavelength of 193 nm is 90% or more.

Next, a method of manufacturing a silica glass member according to the present invention will be described.
The method for producing a silica glass member according to the present invention comprises the steps of producing silica glass which is a transparent vitrified dense body, and for the silica glass to 50 μm from the surface of the silica glass surface perpendicular to the light transmission direction. Doping the fluorine so that the content of fluorine in the region is 1.0 wt% or more and 5.0 wt% or less, and an annealing treatment step of heating at less than 1000 ° C. in the air after the fluorine doping step; It is characterized by including.

For example, the direct vibratization method or the VAD method is used to prepare a transparent vitrified dense silica glass, and then heat treatment is performed in a fluorine compound gas and under pressure to form a region of 50 μm or less from the surface (lithography light In the region from the surface of the silica glass surface perpendicular to the permeation direction to the depth of 50 .mu.m), the fluorine content is 1.0 wt% or more and 5.0 wt% or less.
In addition, although the method of processing the gas doping to a dense body in a hydrogen atmosphere is disclosed in JP 2005-336047 A, the doping method of fluorine compound gas to silica glass which is a dense body is known. Absent. It is presumed that this is because fluorine atoms are larger than hydrogen atoms and thermal diffusion is insufficient.

Further, the step of doping fluorine is specifically described.
In the step of doping the fluorine, it is desirable that the treatment temperature when doping the fluorine into the silica glass be performed at the annealing temperature or more of the glass. The annealing point is preferably a temperature of 1300 ° C. or more and 1650 ° C. or less at which the viscosity of the glass is 10 ¹³ dPa · s or less.
When processing below this temperature, a fluorine concentration will be less than 1.0 wt%. Furthermore, in order to make the fluorine concentration more than 5.0 wt%, treatment at 1650 ° C. or higher is necessary, but in this case, deformation of the glass occurs and it is difficult to obtain silica glass as a member.

The effect of doping is also related to the stress on the glass surface, and it is desirable to quench the glass before doping.
Quenching heats the silica glass at a temperature range of 1000 ° C. to 1500 ° C. and a viscosity of 10 ^14.5 dPa · s or less, preferably 10 ^13.0 dPa · s or less, and then the silica glass is heated to 800 ° C. It says to quench to the following.
For example, it can be carried out by holding the silica glass in the air atmosphere at 1400 ° C. or more for one hour or more and then quenching it by pulling it out of the furnace body or the like. In this case, stress occurs in the entire silica glass, but in particular, residual stress occurs in the glass surface. Fluorine doping is preferable because it is a chemical annealing treatment and its effect is easily exhibited when the residual stress is large.

Further, fluorine doping is performed by heat treatment in a fluorine compound gas atmosphere and under pressure. Specifically, fluorine doping is promoted by heat treatment under a fluorine compound gas atmosphere and under pressure of 1.0 to 2.0 atmospheres (gauge pressure, hereinafter the same).
Here, the width of the maximum value and the minimum value of the fluorine concentration in the region up to 50 μm from the surface of the silica glass surface does not become 100 ppm or less when the pressure is less than 1.0 atmospheric pressure or higher than 2.0 atmospheric pressure, and partial thermal expansion This is not preferable because it causes a difference.

Further, SiF ₄ gas can be used as a fluorine compound gas used for fluorine doping. The fluorine compound gas may be 100% SiF ₄ gas, or a mixed gas of SiF ₄ gas and He gas, or the like.
Further, the introduction temperature of the mixed gas is desirably 1300 ° C. or more and 1650 ° C. or less.
In the case of processing below this temperature, the fluorine concentration is less than 1.0. Furthermore, in order to make the fluorine concentration more than 5.0 wt%, treatment at 1650 ° C. or higher is necessary, but in this case, deformation of the glass occurs and it is difficult to obtain silica glass as a member.
In addition, the fluorine concentration in the silica glass member obtained can be made 1.0 wt% or more and 5.0 wt% or less by adjusting the concentration ratio of the SiF ₄ gas in the mixed gas.

  In addition, since the fluorine concentration and the OH group concentration are in a trade-off relationship, the OH group concentration is 1.0 wt% or more and 5.0 wt% or less in the region from the surface of the silica glass surface to 50 μm. It is desirable that it is 10 ppm or less.

In addition, after the fluorine doping process, an annealing process of heating at less than 1000 ° C. in the atmosphere is performed.
This annealing step is performed to bring the fictive temperature to 1000 ° C. or less. That is, in order to set the thermal expansion of the silica glass surface layer to 4.0 × 10 ⁻⁷ / K, it is desirable to set the fictive temperature to 1000 ° C. or less.

In addition, by setting the fluorine content to 1.0 wt% to 5.0 wt% in the fluorine doping step, the viscosity can be reduced, and annealing can be performed at a lower temperature. Moreover, since the annealing treatment is performed at a lower temperature, the distribution of the fluorine content in the silica glass does not change during the annealing treatment, and the homogeneous fluorine content can be maintained.
The annealing treatment needs to be performed at a temperature of less than 1000 ° C. and a viscosity of 10 ^14.5 dPa · s or less. The annealing temperature is determined by the temperature characteristics of silica glass.
For example, since the strain point of silica glass having a fluorine concentration of 1.0 wt% or more and 5.0 wt% or less is less than 1000 ° C., the annealing temperature is usually less than 1000 ° C., preferably 800 ° C. or less, more preferably 600 ° C. From 400 ° C.

  EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited by the examples shown below.

Example 1
A silica glass was deposited by causing a hydrolysis reaction with an oxygen gas in a flame using silicon tetrachloride gas as a raw material to form an ingot of φ250 × 500 mm.
The obtained silica glass ingot is cut into a sample glass plate of 152 mm long and 6.4 mm thick, and then held at 1,400 ° C. in the air atmosphere for 1 hour, and then pulled out of the furnace body for quenching treatment Did.
Thereafter, the region 50 μm from the surface of the silica glass was subjected to fluorine doping treatment by treatment in silicon tetrafluoride gas under a pressure of 1.2 atm for 1 hour.
Furthermore, the fictive temperature was controlled by annealing at 800 ° C.

When 50 μm of the surface layer of the produced silica glass plate was etched and the fluorine concentration was measured by chromatography, it was 2.0 wt%.
The region from 50 μm to 100 μm from the surface of the produced silica glass plate was etched and the fluorine concentration was measured by chromatography to be 0.07 wt%.

  Further, when the fluorine concentration of the surface layer up to 50 μm from the surface of the silica glass plate was measured at equal intervals at nine points, the width between the maximum value and the minimum value of the fluorine concentration was 70 ppm.

  The OH group concentration of the 50 μm portion of the surface layer of the produced silica glass plate was measured using a microscopic infrared spectrophotometer, and it was 2 ppm.

The surface 50 μm portion of the obtained silica glass plate was cut, 50 sheets were laminated, and a 2 mm × 3 mm × 2.5 mm sample was prepared, and then thermal expansion measurement was performed with a differential thermal expansion meter.
As a result, the thermal expansion coefficient at 25 ° C. was 3.5 × 10 ⁻⁷ / K.

  Further, a 20 mm × 40 mm × 2.5 mm strip sample was cut out and subjected to optical polishing, and then the linear transmittance at a wavelength of 193 nm was measured by a vacuum ultraviolet measuring device. As a result, the linear transmittance at a wavelength of 193 nm was 91%.

Example 2
After preparing an ingot in the same manner as in Example 1, the sample size was made 152 mm wide × 6.4 mm thick, and after being held at 1300 ° C. in the air atmosphere for 1 hour, quenching was performed by pulling it out of the furnace body. .
Thereafter, the region 50 μm from the surface of the silica glass was subjected to fluorine doping treatment by treatment at 1300 ° C. for 1 hour under 1.5 atmospheric pressure conditions in silicon tetrafluoride gas.
Furthermore, the fictive temperature was controlled by annealing at 800 ° C.

  The surface layer 50 μm of the produced ingot was etched, and the fluorine concentration was measured by chromatography to be 2.5 wt%.

  Further, when the fluorine concentration of the surface layer up to 50 μm from the surface of the silica glass plate was measured at equal intervals at nine points, the width between the maximum value and the minimum value of the fluorine concentration was 76 ppm.

  The OH group concentration of the 50 μm portion of the surface layer of the produced silica glass plate was measured using a microscopic infrared spectrophotometer, and it was 2 ppm.

The surface 50 μm portion of the obtained silica glass plate was cut, 50 sheets were laminated, and a 2 mm × 3 mm × 2.5 mm sample was prepared, and then thermal expansion measurement was performed with a differential thermal expansion meter.
As a result, the thermal expansion coefficient at 25 ° C. was 3.3 × 10 ⁻⁷ / K.

  Further, a 20 mm × 40 mm × 2.5 mm strip sample was cut out and subjected to optical polishing, and then the linear transmittance at a wavelength of 193 nm was measured by a vacuum ultraviolet measuring device. As a result, the linear transmittance at a wavelength of 193 nm was 91%.

Comparative Example 1
After preparing an ingot in the same manner as in Example 1, the obtained silica glass ingot is cut into a silica glass plate of sample size 152 mm wide × 6.4 mm thick, and then it is kept at 1200 ° C. for 1 hour in the air atmosphere. After holding, the quenching treatment was performed by pulling out of the furnace body.
Thereafter, the region 50 .mu.m from the surface of the silica glass was fluorine-doped by treating it in silicon tetrafluoride gas at 1200.degree. C. for 1 hour under the condition of 1.2 atm.
Furthermore, the fictive temperature was controlled by annealing at 600 ° C.

  When 50 μm of the surface layer of the produced silica glass plate was etched and the fluorine concentration was measured by chromatography, it was 0.7 wt%.

  Further, when the fluorine concentration of the surface layer up to 50 μm from the surface of the silica glass plate was measured at equal intervals at nine points, the width between the maximum value and the minimum value of the fluorine concentration was 110 ppm.

  The OH group concentration of the 50 μm portion of the surface layer of the produced silica glass plate was measured using a microscopic infrared spectrophotometer, and it was 12 ppm.

The surface 50 μm portion of the obtained silica glass plate was cut, 50 sheets were laminated, and a 2 mm × 3 mm × 2.5 mm sample was prepared, and then thermal expansion measurement was performed with a differential thermal expansion meter.
As a result, the thermal expansion coefficient at 25 ° C. was 4.2 × 10 ⁻⁷ / K.

  Further, a 20 mm × 40 mm × 2.5 mm strip sample was cut out and subjected to optical polishing, and then the linear transmittance at a wavelength of 193 nm was measured by a vacuum ultraviolet measuring device. As a result, the linear transmittance at a wavelength of 193 nm was 90%.

The silica glass member of the present invention can be suitably used for photolithography using vacuum ultraviolet light such as ArF excimer laser (193 nm) or F ₂ laser (157 nm) as a light source. In particular, it is excellent as a photomask substrate used in a double patterning exposure process using an ArF excimer laser (193 nm) as a light source.

Claims (7)

  Silica glass used in photolithography process using vacuum ultraviolet light as a light source, wherein the content of fluorine is 1.0 wt% or more in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light The silica glass member characterized by being 5.0 wt% or less. The thermal expansion coefficient at 20 ° C. to 50 ° C. is 4.0 × 10 ⁻⁷ / K or less in a region from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light to 50 μm. The silica glass member according to 1.   The silica glass member according to claim 1 or 2, wherein an OH group concentration is 10 ppm or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.   The width of the maximum value and the minimum value of the fluorine concentration is 100 ppm or less in a region from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light to a region of 50 μm. The silica glass member as described in.   5. The silica glass member according to any one of claims 1 to 4, wherein the fictive temperature is 1000 ° C. or less in a region up to 50 μm from the surface of the silica glass surface perpendicular to the transmission direction of the lithography light.   The silica glass member according to any one of claims 1 to 5, wherein a linear transmittance of light with a wavelength of 193 nm is 90% or more. Producing a transparent vitrified dense body of silica glass;
A fluorine compound gas atmosphere and an additive such that the content of fluorine is 1.0 wt% or more and 5.0 wt% or less in the region from the surface of the silica glass surface perpendicular to the transmission direction of lithography light to 50 μm to the silica glass Heat treatment under pressure and doping with fluorine;
An annealing treatment step of heating at less than 1000 ° C. in the atmosphere after the fluorine doping step;
A method of manufacturing a silica glass member, comprising: